1. FIELD OF THE INVENTION
The present invention relates to a diathermic dissector for dissecting living tissues by flowing high-frequency current over a wire, or more particularly, to a diathermic dissector with a bifurcation forming a path having substantially the same cross-sectional area as a lumen for guiding a wire.
2. DESCRIPTION OF THE RELATED ART
Diathermic dissectors for endoscopes have been employed in recent years. Herein, an insertion tube of an endoscope is guided to a body cavity, a flexible sheath characteristic of electric insulation is routed through a channel formed in the insertion tube, a diathermic dissecting section formed with a conducting wire exposed at the tip of the flexible sheath is pressed on a therapeutic region, then high-frequency current is supplied to flow through the conducting wire to dissect an intended living tissue.
Of the foregoing diathermic dissectors, an endoscope diathermic dissector disclosed in Japanese Unexamined Utility Model No. 61-156911 is well-known. FIG. 1 shows the distal portion of the endoscope diathermic dissector.
In FIG. 1, on a side wall in the terminal (distal) portion of a flexible sheath 91 made of electrically-insulating material, a pair of openings or side holes 92a and 92b are bored in the longitudinal-dislocated manner to penetrate through a first lumen 93 for guiding a wire. A conducting wire 94 is routed through these side holes 92a and 92b so that the conducting wire 94 will come out of the flexible sheath 91 between the side hole 92a and the side hole 92b. The exposed portion of the conducting wire 94 forms a diathermic dissecting section 95.
The tip of the wire 94 is provided with a locking member 96. With the locking member 96, the wire 94 is locked in the distal end of the first lumen 93. As shown in FIGS. 1 and 2, the flexible sheath 91 has a second lumen 97 running in parallel with the first lumen 93, allowing a guide wire, which is not shown, or other guide member to pass through, and serving as a fluid feed path for feeding contrast medium.
As shown in FIG. 3, the proximal end of the flexible sheath 91 is connected to a bifurcating section 98 for bifurcating the flexible sheath into a first duct 98a for guiding the wire 94 and a second duct 98b connected to the second lumen 97. A base 99 is attached to the end of the second duct 98b.
The wire 94 is connected to an operation member, which is not shown, at the back of the first duct 98a from which the wire 94 comes out. When the operation member is advanced or withdrawn, a dissecting section 95 of the wire 94 projects or part of the sheath in which the dissecting section 95 is formed bends. A wire exposing itself outside at the opening is pressed onto a tissue of a therapeutic region. With high-frequency current supplied by surgeon's manipulation, the tissue is cauterized and dissected.
To feed contrast medium through the second lumen 97, a syringe (not shown) must be mounted on the base 99.
In an endoscope diathermic dissector having the aforesaid configuration, when a therapeutic region is to be dissected, an operation member is advanced or withdrawn to expose a wire 94 of a dissecting section 95 or project the corresponding portion of a sheath so that the wire will touch the therapeutic region.
In the aforesaid configuration of prior art, a space 100 of a first duct 98a for guiding a wire 94 is so large that even when an operation member is, for example, advanced, the wire 94 buckles up in the large space 100 (as shown with an alternate long and two short dashes line in FIG. 3).
Therefore, advancement by a surgeon's manipulations is not fully communicated to the distal end of the wire 94. As a result, the dissecting wire section exposed outside at the opening cannot be projected to form a shape most suitable for dissection. This results in insufficient operability. When a wire buckles up, the wire must be stretched (withdrawn) once, then advanced.
When buckling occurs, even if the wire 94 is stretched, bending distortion cannot be dissolved quickly. Advancement and withdrawal must be repeated to shape the wire as desired. When advancement and withdrawal are repeated, buckling often recurs. When buckling is repeated, great distortion occurs in the buckled area. The wire 94 becomes prone to rupture, deteriorating durability.
In other cases, when an operation member is withdrawn, the distal portion of a sheath 91 in which a dissecting section 95 is formed is curved to form an arc. This allows a portion of a wire 94 exposing itself outside or the dissecting section 95 to project for use in dissecting an object tissue. After dissection is complete, the operation member must be advanced to straighten the curved area. During the advancement, the wire 94 of prior art buckles up in a large space 100 as described above. This results in degraded operability and deteriorated durability of the wire 94.
During cleaning, the operation member is advanced and withdrawn repeatedly. In prior art, the cleaning causes the wire 94 to buckle up in the large space 100 as described previously.